The present invention relates to solid solutions of monoazo pigments having desirable shade and colour strength characteristics. In particular the present invention relates to novel solid solutions of monoazo pigments, a process for their manufacture and their use in printing inks, ink varnishes, dyes and plastics compositions.
X-rays are electromagnetic radiation corresponding to a wavelength of approximately 100 picometers. When this radiation is passed through a crystalline material, diffraction can occur if the Bragg law is satisfied:
xcex=2d sin xcex8
Where xcex is equal to wavelength of the x-ray radiation, d is the spacing between the lattice planes and xcex8 is the glancing angle, i.e. the angle the incident radiation makes with the lattice plane. When this technique is used on a powder sample it is known as powder X-ray diffraction (XRD), and is often used as a fingerprint in the identification of crystalline solids. Indeed a database of over 30,000 such diffraction patterns is maintained by the Joint Committee on Powder Diffraction Standards. Not only will different compounds generally exhibit different diffraction patterns, but different crystalline phases (polymorphs) of the same material will exhibit different patterns. Powder X-ray diffraction is particularly suitable for the identification of organic pigments, as they are most often prepared as powders of varying degrees of crystallinity. Each organic pigment provides a different diffraction pattern allowing easy determination of the identity and crystallinity of a sample.
It is common in the organic pigment industry to purposely prepare mixtures of different pigments to enhance specific desired properties such as shade and colour strength. Such mixtures can fall into three categories:
1. Simple physical mixtures where there are at least two species of different crystal structure. The resultant diffraction pattern of such a physical mixture of materials is simply the combination of the XRD of one sample overlaid on the XRD other material(s) XRD. In such cases it is possible to estimate the relative concentrations of each material in the mixture by analysis of the XRD.
2. A host-guest solid solution may be formed. In this case the crystal lattice of one of the materials acts as a host to the other material(s), which, instead of adopting its own unique crystal lattice is present as a guest in the lattice of the host material. In this case only the X-ray diffraction pattern of the host material is observed.
3. A new crystal form is produced by the mixing of two or more compounds. In this case the X-ray diffraction pattern corresponds to none of the individual materials present, but is a new and unique pattern.
The present invention relates to host-guest solid solutions and in particular the synergistic effects produced by the formation of solid solutions of monoazo pigments. Such effects are desirable as they provide improvements in the properties of such pigments. In particular the solid solutions of monoazo pigments according to the present invention provide improvements in colour strength, dispersion, gloss, increased transparency and a deeper masstone in inks, and improved heat stability in plastics.
The formation of solid solutions of diarylide yellow and high performance organic pigments is known for diarylide yellows and is documented Dyes and Pigments, 1992, 18, 69 and for high performance pigments in EP-A 704,497, EP-A 358,148 and EP-A 73,463. The effect of forming solid solutions of pigment materials is generally to form smaller crystals. Such changes in the crystal morphology are known to affect the colour strength, hiding power, heat stability and dispersion characteristics as discussed Chemical Society Reviews, 1997, 26, 203. The decrease in particle size is also thought to contribute to the depth of the masstone. The prior art method for the preparation of solid solutions of diarylide pigments requires the utility of two coupling materials and a single amine component. The prior art method for the preparation of high performance pigments is a multi-stage synthesis which does not involve a diazotisation reaction.
However the present invention relates to novel solid solutions of classical monoazo pigments which are formed by a process which requires the use of a single coupling component and at least two different amine materials which may be diazotised together. The present application provides a process for the formation of these novel monoazo pigment solid solutions and also demonstrates the technical advantages these solid solutions give over both the pure host material alone, as well as their advantages over a physical mixture of the solid solution components.
The present invention provides novel solid solutions of monoazo pigments comprising a host lattice and at least one guest material wherein the host lattice is a materials having the general formula I or II, wherein compound of formula I is defined as 
and wherein R1=H, CO2 or CO2R, where R may be phenyl which can be substituted one to three times with the following substituents: C1-C4alkyl such as methyl, ethyl, n-, i-propyl, n-, i-, sec.- or tert.butyl, preferably methyl, C1-C4alkoxy such as methoxy, ethoxy, n-propoxy, n-butoxy, preferably methoxy, halogen such as Cl, Br or I, preferably Cl, NO2 or xe2x80x94NHC(O)CH3, R2, R3, R4, R5 and R6, independently from each other may be C1-C20alkyl, C1-C20alkoxy, C2-C20alkenyl, C1-C20alkylthiol, C1-C20alkoxycarbonyl, hydroxyC1-C4alkoxy, phenyl, benzyl, phenylthio, halogen such as fluoro, chloro, bromo, iodo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94CF3, xe2x80x94COR7, xe2x80x94COOR7, xe2x80x94CONR7R8, xe2x80x94SO2R7, xe2x80x94SO2NR7R8, xe2x80x94NR7NR8 or xe2x80x94OR2 in which each R7 and R8 are each independently H, C1-C4alkyl or phenyl; M2+ is an earth alkaline metal cation such as Ca2+, Mg2+, Sr2+, Ba2+ or Mn2+,
and wherein formula II is defined as 
wherein R9 stands for C1-C20alkyl, C1-C20alkoxy, C2-C20alkenyl, C1-C20alkylthiol, C1-C20alkoxycarbonyl, hydroxyC1-C4alkoxy, phenyl, benzyl, phenylthio, halogen such as fluoro, chloro, bromo, iodo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94CF3, xe2x80x94COR7, xe2x80x94COOR7, xe2x80x94CONR7R8, xe2x80x94SO2R7, xe2x80x94SO2NR7R8, NR7NR8 or xe2x80x94OR2 in which each R7 and R8 are each independently H, C1-C4alkyl or phenyl,
and wherein the guest material(s) have the same general formulae as their respective hosts with the proviso that they differ in molecular structure at at least one position from the respective hosts, i.e. at least one substituent R1 to R9 is chosen differently.
The solid solutions according to the present invention comprise a host material and at least one guest material which is incorporated in the lattice of the guest material. The X-ray diffraction pattern of the solid solutions according to the present invention arexe2x80x94according to observations up to nowxe2x80x94equivalent to the X-ray diffraction pattern of the host material.
The limit of detection of one crystal phase (the guest material) in another (the host material) by powder X-ray diffraction is approximately 10%. It has been assumed herein, that, if at 10%; guest in 90% host a solid solution is formed, then a solid solution will also exist below the detection limit.
The amount of guest material(s) in the host can be chosen in the range of from 1 to 50 mol-%, preferably from 1 to 30 mol-%, more preferably from 5 to 20 mol-%, most preferably from 10 to 20 mol-%, based on the amount of the sum of host and guest. One or more guests, i.e. guest molecules of a different molecular structure, may be incorporated into the same host lattice.
Preferred host materials for use herein are either pigment red 57:1 or pigment yellow 111. 
Preferred guest materials for use herein in a host pigment red 57:1 crystal lattice have the general formula III illustrated below: 
wherein W=SO3H, NO2, or CO2H; X=Cl, CH3, SO3H, CO2H or H; Y=CF3 or H; and Z=Cl, CH3 or H.
Preferred guest materials in the pigment yellow 111 crystal lattice have the general formula IV illustrated below: 
wherein W=SO3H, NO2, OCH3 or CO2H; X=Cl, CH3, SO3H, CO2H or H; Y=CF3 or H; and Z=Cl, CH3 or H.
The final composition of the pigment may include such compounds as are commonly used as pigment additives, for example resins, dyestuffs and/or surfactants. Suitable resins include wood rosin, gum rosin, tall oil rosin, hydrogenated rosin, rosin esters, disproportionated rosin, dimerised rosin, polymerised rosin, phenolic rosin and carboxyl containing maleic or fumaric resin. The proportion of resin may vary over a wide range and may be for example 0.1 to 50% by weight based on the weight of the inventive pigment.
Suitable surfactants include anionic, cationic, amphoteric or non-ionic surfactants. Anionic surfactants which may be used are e.g. alkyl-, aryl- or aralkyl sulphates or sulphonates; alkyl-, aryl or aralkyl phosphates or phosphonates; or carboxylic acids. Cationic surfactants which may be used are e.g. primary, secondary or tertiary amines or quaternary salts of amines. Non-ionic surfactants which are suitable for use include long chain alcohols, alcohol or amine/ethylene oxide condensates, amine oxides or phosphine oxides and other castor oil derivatives. The amount of surfactant may vary over a wide range and may be, for example, 0.1 to 20% by weight based on the weight of the inventive pigment.
When a dyestuff is present, it is usually a water soluble version of the pigment containing such water solubilising groups as carboxyl or sulphonic acid groups. The amount of dyestuff may be from 1 to 20% by weight based on the weight of the inventive pigment.
The solid solutions of monoazo organic pigments according to the present invention are suitable for application in printing inks including oil inks and liquid inks, in particular liquid packaging inks, solvent based and aqueous paints and plastics. Such solid solutions may show in an improvement in one or more of the following properties depending on the application medium: dispersion, gloss, colour strength, transparency, and heat stability.
By way of illustration, the following methods may be used to prepare the solid solutions of the invention:
1. A mixture of amines appropriate to the solid solution being prepared is diazotised and is added to an aqueous solution or suspension of coupling components and surface treatments. Once coupling is completed the preparation is finished by appropriate pH adjustment and heat treatment.
2. A mixture of amines appropriate to the solid solution being prepared is diazotised and is added to an aqueous solution or suspension of coupling components. Once coupling is completed the preparation is finished by addition of appropriate surface treatments, pH adjustment and heat treatment.
3. A mixture of amines appropriate to the solid solution being prepared is diazotised and is added simultaneously with an aqueous solution or suspension of coupling components and surface treatments. Once coupling is completed the preparation is finished by appropriate pH adjustment and heat treatment.
4. A mixture of amines appropriate to the solid solution being prepared is diazotised and is added simultaneously with an aqueous solution or suspension of coupling components. Once coupling is completed the preparation is finished by addition of appropriate surface treatments, pH adjustment and heat treatment.
5. In addition to the methods detailed above the diazo components may be prepared separately, by the same or different methods and combined prior to coupling or added simultaneously to the coupling vessel.